The shaping of plastic articles and plastic laminated articles as well as wood and other construction materials is well known in the art.
The following list involves a number of prior art devices which have been used for shaping materials.
Rendall, U.S. Pat. No. 335,309--Cutter Head--Describes a cutter head for cutting down trees or other structures in which the cutting teeth are aligned in a spiral around a shaft and the chisel-like teeth on the spiral are rotated by the shaft and chop out the material being cut. A configuration is described for one modification in which there are two spiral configurations to the teeth; one running in one direction and the other the opposite direction on the shaft so that wood chips being formed are thrown outward from the area being trimmed.
Blanco, U.S. Pat. No. 1,630,602--Reamer--Describes a tapered reaming tool having four sets of teeth which are alternately aligned upward cutting and downward cutting for the purposes of cleaning up and/or shaping the bore of an already drilled hole "without the necessity of turning the reamer at an excessive speed." The reamer is not used to trim the edges of flat pieces and is designed to fit inside a bored hole to smooth and enlarge the interior walls of the hole.
Compton, U.S. Pat. No. 2,623,553--Side Cutting Rotary Tool--Describes a rotatable bit for rapid side cutting having a longitudinal groove with cutting teeth located on the edge of the groove. The device is designed to drill a hole and then to be used to cut or scroll sideways.
Cave, U.S. Pat. No. 3,058,199--Cutting Tool--Describes a bit having a spiral groove from the cutting point to the shank end and teeth protruding from the cylinder of the bit to provide rasping or abrasive force on the side of a drilled hole. The tool is especially designed for cutting and shaping plastic. The teeth provide for abrasion of plastic material while providing the maximum cooling which is required because plastics soften with heat.
Hunn, U.S. Pat. No. 3,327,749--Transverse Cutting Rotary Tool Bit--Describes a bit having a plurality of longitudinal grooves which is designed first to drill a hole and thereafter to make a transverse cut. The transverse cutting action is facilitated by the staggered configuration of teeth located along the length of the bit.
Maday, U.S. Pat. No. 3,913,196--Rotary Cutting Tool--Describes a router tool for trimming and cutting plastic materials that may fray if cut with other routing bits. The cutting edges are two pairs of opposed helical cutting edges, one pair starting on the shank of the bit and the other pair at the drilling end of the bit, each of which meets in the middle of the bit shaft. Each of the helical cutting edges terminate at the middle of the bit which is also the working center of the bit. Materials to be cut must be centered on the working center of the bit so that when the tool is rotated, the cutting edges on opposite sides of the working center are opposed in their spiral direction. They cut the material with a cutting action in which the top and bottom helical cutting edges cooperate to simultaneously apply a compressive cutting force to the edge of the material being trimmed.
As is indicated by Maday, most plastics can be trimmed or cut with conventional routing tools but laminated material containing fabric reinforcements present problems. Composite laminates made with high strength fibers are particularly difficult to machine or trim along their edges without generating a fuzzy, frayed-looking edge. Maday has provided one type of such drill in U.S. Pat. No. 3,913,196. However, as mentioned above, his cutting tool requires that the piece being worked be centered at the center of the working zone of the tool in order to trim the edges and obtain a fuzzy-free edge. If the piece is not properly aligned to engage the working center or, as he calls it, the zone of confrontation, then the compressive action from above is not engaged.